The present invention relates generally to latches, and in particular to power unlatching latches used in passenger doors of vehicles.
Power unlatching latches (also known as power release latches) are known. Latches typically include a latch bolt in the form of a rotating claw which is held in a closed position, or a first safety position, by a pawl (also known as a detent). The pawl can be rotated by operation of a door handle to rotate the claw when the door is opened. Various systems are known whereby the pawl can additionally be rotated by an actuator, typically an electric motor.
A drawback to electric motors is that they can fail in service. Sometimes, motor failure occurs when the latch is fully closed, and sometimes motor failure occurs when the latch is fully opened. In the former case, the latch must then be manually opened. Typically, motor failure will be immediately apparent to the user since the handle load will increased. In the latter case, it may not be possible to relatch the door, but again, this is immediately apparent to the user.
Motor failure can also occur partially through an opening sequence. Under these circumstances, it is possible to finish the opening sequence by manual operation of a door handle. It is also possible to properly relatch the latch upon closing of the door. However, while the door may remain closed, the latch mechanism (typically a latch pawl engaging a rotating claw latch bolt) may not be fully engaged, and there is a risk that the door may unexpectedly and suddenly open when the vehicle is in use, creating a safety hazard for the vehicle occupants.